Re-hello Iseemtobeaverb
Well, you'll have to be more familiar with the template hierarchy of wordpress. As Srikat told you, you can't use "category_auction.php" as is...
http://codex.wordpress.org/Templates_Hierarchy
As Srikat suggest, you could use the conditonals tags in your category page.
http://codex.wordpress.org/Conditional_Tags
On my side, I prefer to keep the things separate.
So, if you see the template hierarchy :
category.php will be used to display all categories.
If you want a special file for your category, you have to name this file with the category ID (the number associated with the category in your wp-admin manage category section)
Let's say your category auction is number 14...
So, your category file will be : category-14.php
===
For different single page, this is how I do it :
You will need three files. Your normal "single.php"... Then, make two other files. One named "single_normal.php" and the other, as you did "single_auction.php"
With the template hierarchy, you can understand that worpress will always call "single.php" whenever you want to see a single post.
So, in the "single.php", you can use a conditional tag like this.
<?php
if (in_category('14')) {include (TEMPLATEPATH . '/single_auction.php');
}
else { include (TEMPLATEPATH . '/single_normal.php');
}
?>
This is all you need in this file. In english, it means : if we are in the category 14, get and display the "single_auction.php" file. Else, if we are in any other category, get and display the "single_normal.php" file.
Of course, you adjust the (in_category('14') to fit your category id...
You follow me ? You only use single.php like a switch, to ask wordpress to use a file or another...
At this point, you can figure what to do next... Use your "single_normal.php" to display your "normal" content that you want in all your blog, and use "single_auction.php" to display what you want for posts under the auction category... The category 14... Your auction_sidebar.php for instance and wathever you like.
There is almost nothing you can't do with wordpress and the conditional tags, as long as you respect the template hierarchy... You must understand how wordpress "think", then you know how to ask him to fit your special needs... :-)
S.